The field of the invention generally pertains to wire drawing and collection machines. The invention relates more particularly to a double-draft wire drawing and collection machine with tension-sensitive speed control.
Various types of wire drawing machines have been developed to mass produce large quantities of wire in a wide variety of gauges. In particular, continuous wire drawing machines have greatly improved wire production by incorporating consecutively arranged multiple reduction dies. This increases the number of passes or drafts experienced by wire rod, and consequently enables greater wire gauge reductions.
For example, in U.S. Pat. No. 2,272,195 an accumulating-type continuous wire drawing machine is shown having multiple reduction dies arranged in series with corresponding advancing blocks or drums positioned to successively draw wire through the respective dies. Each block is driven by a variable-speed motor controlled by an independent speed control rheostat. The block furthest downstream, known as the finishing or "master" block 20, is preset to run at a constant speed, while the speed of each block preceding the master block can be independently regulated to compensate for wire elongation, as well as to control the amount of accumulation on each block. In the '195 patent, these block speeds are manually adjusted by an operator observing the motion of guide rings 45, 45a and chains 46, 46a slidably mounted on each respective block.
However, most continuous wire drawing machines in operation today, especially non-accumulating type machines, utilize tension control arms, i.e. dancers to automatically and independently regulate the speed of corresponding motors and advancing blocks. They function to maintain constant wire tension and prevent wire breakage by detecting wire tension differentials between reduction dies. They are typically connected to rheostats which generate and transmit proportional electrical control signals to the motor of the corresponding advancing block or drum. In this manner a master block having a preset speed can reference the speeds of each of the preceding advancing blocks, and prevent wire breakage between reduction dies.
Additionally, various types of wire collection machines or "take-up" equipment have been developed to support wire drawing machines in the final packaging/bundling stage of wire production. In particular, wire collection machines known as "dead blocks" have been widely used to coil and collect wire into bundles. They do so by means of a rotary "flyer" mechanism which operates to coil or wrap wire around a stationary block or drum. Due to a taper on the stationary block, wire wrapped in this manner continues to move outward on the stationary block while maintaining sufficient tension to pull evenly, until the wire falls into a finished wire heap. The advantage of this is that wire can be coiled and removed with complete safety, regardless of coil speeds, and without interrupting the operation of the drawing machine.
In many cases an additional die is secured to the flyer to simultaneously draw and coil wire on the stationary block. This enhances the utility of the dead block by complementing wire drawing machines to produce even greater wire reductions. Moreover, because of their combined wire drawing and collection capabilities, these dead block machines can also be utilized as stand-alone production units capable of directly drawing wire rod from a spool, and not merely as ancillary equipment to wire drawing machines. One example of a dead block machine used as a stand-alone unit is a fixed double-deck dead block having a single block with two deck surfaces. While double-deck dead blocks operate to draw and collect wire as a single production unit, they typically have relatively slow operating speeds, and have a limited range of wire gauge reduction. Additionally, because double-deck dead block machines are driven by a single motor they cannot take advantage of the tension control arm feature described above.